This project seeks to explore the consequences of the modification of DNA by carcinogens and mutagens by use of bacterial systems to determine the changes in nucleotide sequence that occur in the progeny of infectious DNA molecules that carry single, site-specific carcinogen moieties, i.e. site- directed mutagenesis. Novel synthetic oligonuceotides that contain only a single guanine will be modified by reaction with synthetic reactive aromatic amines. The adduct will be characterized and introduced into both pBR322 plasmid and M13 bacteriphage DNA so as to retain the ampicillin resistance of pBR322 for clonal selection, and the possibility of utilizing the M13 galactosidase system for phenotypic detection of mutants. Restriction analysis will be used to verify the structure of the product. Plaques or clones produced by introduction into appropriate bacterial hosts will be detected hybridization to probes that overlap the site of the adduct. Additionally, changes in the ability of the M13 bacteriophage to complement the host cell galactosidase peptide will permit direct identification of mutants that have resulted from other base substitutions. The nucleotide sequences of the mutants will be determined be Sanger's technique. By this approach we wish to clarify the following questions. 1) How do the structures of aryl moieties on the C-8 of DNA guanine influence the mutations produced by arylamines? 2) Are there differences in the mutagenic responses of the pBR plasmid and the M13 bacteriophage? Are mutations independent of the strand (i.e. plus or minus) to which the adduct is attached, or whether the adduct is single- or double-stranded when introduced into the cell? 3) What are the influences of repair systems of the host cell on the mutations that are produced? These studies will provide insight into mechanisms by which mutagens and carcinogens can alter the informational content of DNA and aid in the development of systems and approaches that can be used in the study of gene expression, as well as to explore the potentials of these compounds to produce similar effects in mammalian cells.